Human Factors Study to Validate the User Interface of TOBI Podhaler Using Placebo Capsules: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Human Factors Study to Validate the User Interface of TOBI Podhaler Using Placebo Capsules (NCT03502070), a na phase 4 study. The primary outcome is Number of Participants With Critical Use Errors and Close Calls Associated With the Simulated Inhalation of One Dose Using TOBI Podhaler.

2. Clinical Question

This is a human factors question about whether intended users can follow key steps while using the interface in a simulated setting. The primary outcome is expressed as a count of participants with critical use errors and close calls, not as a comparison of clinical outcomes between treatment groups. The registry record does not report the observed primary outcome count, so it does not show how many participants experienced an error or close call. The record also does not report a separate measure of successful use or any comparison with another device.

3. Trial Design

The registry record describes a multicenter, phase 4, single-group study. Its official title identifies the intended population as people with cystic fibrosis aged 6 years and older. The listed enrollment is 47 participants. The study is marked completed, with a start date of 2018-06-26 and a primary completion date of 2019-03-19.

The study used an open-label placebo arm. Its arm description says participants used one dose, consisting of 4 placebo capsules. The interventions list placebo as a drug and TOBI Podhaler as a device. In this context, the placebo capsules supported the simulated inhalation task; the study is described as validating the device interface, not as testing the clinical effect of active medication.

The record identifies allocation as not applicable, masking as none, and the model as single group. There is therefore no randomized treatment contrast to interpret. The placebo arm is not a separate comparator against which the device can be compared, and the recorded design does not establish a like-for-like control comparison.

The primary outcome timeframe is 1 Day. It concerns the number of participants with critical use errors and close calls associated with simulated inhalation of one dose. The endpoint description lists specific handling and inhalation steps that could contribute to an error or close call. The registry record does not report the detailed assessment procedures, the criteria used to classify an event as critical, or how close calls were distinguished from errors. Those protocol details are not reported in the registry record.

The record lists one outcome measure but no posted analysis. It does not report the primary endpoint result, an analysis population, or the statistical model used to summarize the outcome. The study’s completed status does not itself supply those missing results. Interpretation must therefore remain focused on the design and the information that is actually posted.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Overall Study

Reasons for not completing this period:

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

6. Primary Endpoint

The registry lists the primary outcome as Number of Participants With Critical Use Errors and Close Calls Associated With the Simulated Inhalation of One Dose Using TOBI Podhaler, measured over 1 Day.

The primary endpoint counts participants who had critical use errors and close calls during simulated inhalation of one dose using the TOBI Podhaler. The measure is reported in participants, and its timeframe is 1 Day. The listed actions span several stages of device use: placing a capsule, replacing the mouthpiece, piercing the capsule, releasing the device before inhaling, inhaling with an adequate seal and technique, using a reserve device when needed, administering 4 capsules per dose, and avoiding swallowing the capsule.

This kind of endpoint is intended to assess whether people in the intended user population can carry out important steps with the interface. It differs from an endpoint measuring a biological or clinical response to active treatment. A count of participants with an error or close call can describe how often the assessment identified a potential use problem, but interpretation depends on the event definitions and assessment procedures. Those details are not reported in the registry record.

The registry record does not report the observed primary endpoint count. Consequently, the posted information does not establish how many participants had an error or close call, which listed steps were involved, or how often individual events occurred. The endpoint description alone defines what was intended to be counted; it is not a result.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry record describes a binary outcome in terms of participants with an event: the primary measure is a count of participants with critical use errors and close calls. That distinction is important. The measure is not a count of every individual error, nor does the record give a separate total for each listed type of error. A participant could encounter one or more of the listed problems, but the posted endpoint wording identifies the participant-level count as the primary measure. The registry record does not explain how multiple events for one person were handled in the analysis.

What does a participant count tell us?

A participant count is a descriptive summary of how many people met the endpoint definition in the assessed group. To interpret it as a proportion or rate, the result must be considered alongside the number of participants assessed. The primary endpoint denominator is not reported in the registry record, and the numerator is not reported either. The listed enrollment of 47 is not enough to reconstruct the number assessed: the record does not provide participant flow or confirm that every enrolled participant contributed an endpoint observation.

In general, binary outcomes can be summarized as counts and proportions, and uncertainty can be described with a confidence interval. A confidence interval gives a range of values compatible with the data under the method used; it is not a guarantee that the true value lies within that range. Here, no primary outcome estimate or confidence interval is reported, so the reader cannot assess the endpoint’s statistical precision. No test result or p-value for the primary outcome is reported either.

Why does the design constrain statistical comparisons?

This study is recorded as single group, with allocation not applicable and no masking. The registry record therefore does not identify a randomized contrast between two groups. General methods for comparing treatment groups would not create a valid comparator where the design has none. The placebo capsules were part of the simulated-use assessment, not a separate control group. The primary question is descriptive: whether participants encountered the specified use errors or close calls while using the interface in the study setting.

General statistical models are chosen to match the outcome, design, and available data. For a participant-level binary endpoint, an analysis might summarize the event count and the number assessed, but the registry record does not report which analytical approach was used. It also does not report adjustment variables, a model specification, a confidence-interval method, or a prespecified decision threshold. None should be inferred from the endpoint type alone.

How should the sample-size illustrations be read?

The page includes a sample-size section, but those values are planning illustrations rather than a description of the trial’s original design or observed power. The stated illustration assumptions are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the effect to detect is described as a fraction of the observed effect. These assumptions describe a hypothetical two-arm planning exercise. They do not match the posted single-group design, which has no randomized comparison.

General sample-size planning asks how many participants would be needed to detect a specified effect under stated assumptions. An illustration can change when the assumed effect, allocation, or statistical method changes. Such a calculation is not evidence that the completed study had a particular probability of finding an effect, and it cannot replace a reported outcome analysis. The registry record does not report a sample-size justification for the actual study, the effect used in its original planning, or a trial-specific power calculation. The primary outcome result is also not reported, so the posted information does not support interpreting an observed effect for planning purposes.

The registry record lists no posted analyses. That does not establish that no analysis was conducted; it means the record does not include an analysis result in the information. The endpoint count, denominator, analysis population, handling of missing observations, and statistical method are all not reported in the registry record. As a result, the explanatory statistical reading can clarify what the endpoint and design mean, but cannot reproduce or evaluate an unposted primary analysis.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("Open-Label Placebo")
n      <- c(45)
events <- c(4)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  Open-Label Placebo  45  4  8.9  2.5  21.2  3.5  20.7  3.6  20.8

11. Multiplicity, Missing Data and Analysis Populations

The registry record lists one outcome measure and no posted analyses. It does not report a formal plan for multiplicity, including whether the listed use-error categories were considered separately, whether any outcomes were ordered in a testing hierarchy, or whether an adjustment for multiple statistical tests was planned. The endpoint description names several types of critical use error and close call, but that list does not establish that each type was analyzed as a separate outcome.

Missing-data handling is not reported in the registry record. The record does not say whether any enrolled participants lacked an endpoint assessment, how incomplete assessments were treated, or whether participants were excluded from an analysis. The listed enrollment of 47 should not be treated as the primary endpoint analysis denominator. The adverse-event summaries list 45 participants at risk, but that denominator relates to the safety figures and does not establish the number assessed for the primary endpoint.

The analysis population is also not reported in the registry record. There is no description of whether the endpoint was summarized for all enrolled participants, only those who attempted the simulated task, or another defined group. The record does not specify a statistical method for the primary outcome or how the endpoint would be interpreted if a participant had more than one listed error or close call.

These gaps limit reproducibility and interpretation. Without a posted analysis population, denominator, missing-data approach, and outcome result, a reader cannot assess whether the reported endpoint—if available elsewhere—covers all participants or only a subset. The absence of posted details is not evidence that the study lacked a prespecified plan; that plan is simply not reported in the registry record.

12. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

Most frequent non-serious adverse event terms

For the Open-Label Placebo group, the registry record lists 45 participants at risk for serious adverse events and 0 affected. It also lists 45 at risk for other adverse events and 1 affected. The number of deaths is 0. These are participant counts in the registry’s safety summary; they are not the primary human factors endpoint.

The serious and other adverse-event categories should be kept distinct. The figures do not describe the number of critical use errors or close calls during simulated inhalation, and they do not indicate which device-use steps were completed correctly. Nor should the count of 1 for other adverse events be combined with the serious-event count: the record presents them as separate categories.

These safety counts do not, on their own, establish whether an event was caused by the placebo, the device, or the simulated-use procedures. The registry record does not provide event terms for the other adverse event or further attribution details. It also does not explain why the safety denominator is 45 while listed enrollment is 47. The denominator should therefore be reported as it appears in the safety summary, without assuming it represents every enrolled participant or the primary endpoint population.

13. What the Result Does, and Does Not, Mean

This study addresses a specific question about the usability of the TOBI Podhaler interface in people with cystic fibrosis aged 6 years and older. Its primary endpoint concerns participants with critical use errors and close calls during simulated inhalation of one dose. That focus differs from a clinical efficacy question: the registry record describes placebo capsules and a device-use assessment, not a comparison of active treatment outcomes.

The record establishes that the study was multicenter, open-label, single group, and completed, with 47 participants enrolled. It also gives a detailed list of device-use actions relevant to the endpoint and reports limited adverse-event counts. These details help explain what the study set out to assess and the context in which it was conducted.

The record does not report the primary endpoint count, its denominator, a statistical estimate, or an uncertainty interval. For that reason, it cannot show how often participants had critical errors or close calls, whether particular steps were more challenging, or how precisely any endpoint frequency was estimated. A missing result is not equivalent to a favorable result or to zero observed errors.

The study also does not provide a comparator group from which to estimate a difference between devices or treatment strategies. The placebo capsules are part of the use task, and the record does not describe a randomized control comparison. Conclusions should therefore stay within the scope of the study’s stated purpose and posted design.

In general, usability findings depend on the users assessed, the task conditions, and the definitions used to classify errors and close calls. The registry record does not give enough detail to evaluate those assessment procedures or determine how well results would transfer to other settings. The posted information supports a description of the research question and record-level design, but it does not support a conclusion about the primary result or a broader claim about device performance.

14. Why This Trial Matters Statistically

Human factors studies use a different kind of evidence from trials that compare clinical outcomes. Here, the central question is whether intended users can carry out important steps with a device interface during a simulated task. The endpoint identifies errors and close calls that may arise while preparing capsules, handling the mouthpiece, inhaling, and completing a dose. These are operational steps, not measures of a clinical response to active medication.

The statistical structure is also important. A participant-level count can describe the frequency of an outcome in an assessed group, but it needs a numerator and an appropriate denominator. The registry record reports enrollment but does not report the primary endpoint result or its analysis denominator. That missing information prevents a reader from assessing the observed frequency or its precision, even though the endpoint itself is clearly named.

The study’s single-group design makes the role of comparison especially clear. A placebo used during a simulated-use task is not the same as a separate control arm. Without a comparator, the design does not estimate a between-group difference. Recognizing this avoids reading a usability validation study as if it were a randomized trial of treatment effect.

The record also illustrates why safety summaries and primary endpoint summaries should not be conflated. The serious and other adverse-event figures are separate from critical use errors and close calls. A safety count cannot fill in a missing usability result, and a missing usability result cannot be interpreted from the safety counts.

Finally, sample-size illustrations require their assumptions to be matched to the question at hand. The planning assumptions described for this page use a hypothetical two-arm framework, whereas this trial is recorded as a single group. These illustrations are useful as planning scenarios, not as evidence of the study’s observed power or as a substitute for its missing primary outcome analysis.

15. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The primary limitation for readers is that the registry record does not report the primary endpoint result. Without the count of participants with critical use errors and close calls, the central question cannot be answered from the posted information. The primary endpoint denominator and statistical uncertainty are also not reported, so neither a frequency nor its precision can be assessed.

The record lists enrollment of 47 participants but does not report participant flow or explain the safety summary’s denominator of 45. It does not establish how many enrolled participants attempted the simulated task or contributed primary endpoint data. The target population is described as people with cystic fibrosis aged 6 years and older, but the characteristics of those enrolled are not reported.

Important assessment details are not reported in the registry record. These include the criteria for classifying critical errors and close calls, how assessors evaluated performance, whether any training or prompts were used, and how repeated errors were handled. The outcome description names relevant actions but does not give the operational definitions needed to judge the classification process.

The design is single group and open label, with no comparator. That design is consistent with a usability assessment but does not support a randomized between-group comparison. The registry record also does not report the analysis population, missing-data approach, statistical method, or a formal multiplicity plan. These gaps restrict assessment of the analysis even apart from the missing result.

Finally, the record’s limited safety counts do not resolve the primary endpoint question and do not establish event attribution. The results cannot be extended beyond the posted study context without further information about the participants, task conditions, and assessment methods.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Human Factors Study to Validate the User Interface of TOBI Podhaler Using Placebo Capsules — NCT03502070.
• Registry record last updated 2022-03-03; status last verified 2022-03.
• Results first posted 2020-06-30.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

19. Record Summary

NCT03502070 is a completed, multicenter, phase 4, single-group human factors study of the TOBI Podhaler interface using placebo capsules. The official title describes people with cystic fibrosis aged 6 years and older. The record lists 47 participants enrolled, an open-label placebo arm, no masking, and a primary endpoint measured over 1 Day.

The primary endpoint is the number of participants with critical use errors and close calls during simulated inhalation of one dose. The registry record does not report the observed primary endpoint count, its denominator, or an analysis result. The listed safety summary for the Open-Label Placebo group reports 0 participants affected by serious adverse events out of 45 at risk, 1 affected by other adverse events out of 45 at risk, and 0 deaths.

The posted design has no comparator group. The registry record does not report the primary analysis method, analysis population, missing-data approach, or outcome precision. The available information describes the study’s purpose and design but does not establish the primary usability result.